Thermally and electrically conducting high index contrast multi-layer mirrors and devices

ABSTRACT

An optical device is provided. The optical device includes a plurality of high index layers. The optical device also includes a plurality of low index layers. The optical device is formed by creating alternating layers of the plurality of high layers and the plurality of low index layers, such that electricity and heat is allowed to be conducted through said optical device.

PRIORITY INFORMATION

[0001] This application claims priority from provisional applicationSer. No. 60/253,910 filed Nov. 29, 2000.

BACKGROUND OF THE INVENTION

[0002] The present invention is in the field of optics, specifically inchanging the characteristics of the resonance of multi-layer Fabry-Perotresonators or 1D Photonic Band Gap.

[0003] Low index contrast multi-layer structures have been fabricated toform VCSELs (Vertical Cavity Surface Emitting Lasers). These low indexcontrast multi-layers have a disadvantage in that their stop bands arevery small, thus requiring more layers to achieve a high reflection.Essentially, these layers may become too bulky to be used with otherintegrated components. On the other hand, high index contrastmulti-layer structures have poor thermal and electrical conductivityproperties. As a result, it is difficult to electrically drive a cavityembedded in a high index contrast multi-layer structure. Furthermore,any heat that is generated in the cavity layer is not easily dissipated.Therefore, it would be difficult to electrically drive light emittingdiodes, lasers or the like in such structures.

SUMMARY OF THE INVENTION

[0004] Accordingly, the invention presents a novel method that willalleviate the problems of poor thermal and electrical conductivity ofhigh index contrast multi-layer systems. Varying the layers of highindex degenerately doped semiconductor and the lower index high thermaland electrical conductivity layers will result in a multi-layerstructure that would permit both electrical injection and thermalstabilization.

[0005] According to one aspect of the invention, an optical device isprovided. The optical device includes a plurality of high contrastlayers. The optical device also includes a plurality of high indexlayers and the plurality of low index layers, such that electricity andheat is conducted through said optical device.

[0006] According to another aspect of the invention, a method forforming an optical device is provided. The method includes providing aplurality of high index layers. The method also alternating layers ofthe plurality of high layers and the plurality of low index layers, suchthat electricity and heat is conducted through said optical device.

[0007] According to another aspect of the invention, a Fabry-Perotdevice is provided. The Fabry-Perot device includes a plurality of highindex layers, and a plurality of low index layers. The Fabry-Perot alsoincludes a top mirror that includes alternating layers of the pluralityof high index layers and the plurality of low index layers, and a cavitystructure that includes a bulk of a selective material. The Fabry-Perotalso includes a bottom mirror that includes alternating layers of theplurality of high index layers and the plurality of low index layers,wherein the top mirror and bottom mirror allow electricity and heat isconducted through the Fabry-Perot device.

[0008] According to another aspect of the present invention, a processfor forming an optical device is provided. The process includes thesteps of providing a plurality of high index layers, and providing aplurality of low index layers, wherein the optical device is formed ycreating alternating layers of the plurality of high index layers andplurality of low index layers, such that electricity and heat isconducted through said optical device.

[0009] According to another aspect of the invention, a method of forminga Fabry-Perot device is provided. The method includes the steps ofproviding a plurality of high index layers, and mirror that includesalternating layers of the plurality of high index layers and theplurality of low index layers, and a cavity structure that includes abulk of a selective material. The Fabry-Perot also includes a bottommirror that includes alternating layers of the plurality of high indexlayers and the plurality of low index layers, wherein the top mirror andbottom mirror allow electricity and heat to be conducted through theFabry-Perot device.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 is a schematic block diagram illustrating the alternatinglayers of high index degenerately doped materials and the lower indexhigh thermal and electrical conductivity materials.

DETAILED DESCRIPTION OF THE INVENTION

[0011] The invention illustrates a device and method of improvingthermal and electrical conductivity of high index contrast multi-layersystems. By alternating the layers in a high index contrast multi-layersystem between high index degenerately doped semiconductor materials andthe lower index high thermal electrical conductivity materials willresult in a system that permits both electrical injection and thermalstabilization.

[0012] The major problem with low index materials is that thesematerials normally exhibit low electrical and thermal conductivity.Thus, it is necessary to find low index materials that possess both awide band gap and sufficient doping to provide a high or hole populationfor thermal and electrical conduction.

[0013] Doped oxides, such as Indium Tin Oxides (ITO) have been known topossess wide band gaps. ITOs also have been commonly used as topcontacts for LED and other electro-optical structures where a conductingbut transparent contact is needed. The ITO's wide-band gap propertyensures that loss in such structures will be due to scattering offcarriers and not to band-to-band transitions. Thus, ensuring that theITO will not exhibit large absorption losses because of its wide-bandgap property. The mixture of tin in ITO acts as a dopant and thedegenerate effects of the doping results in the ITO having a largeelectron density. The invention may utilize other low index materialshaving high thermal and electrical conductivity with doped wideband-gaps, such as doped diamonds. For purposes of illustration, theinvention will be described using ITO as the low index material.

[0014]FIG. 1 is a schematic block diagram illustrating the alternatinglayers of high index degenerately doped materials and the lower indexhigh thermal and electrical conductivity materials. The invention is adevice that includes a multi-layer optical micro-resonator device 2 thatfurther includes any number of alternating high index layers 10, 12, 14,15, 17, and 19 and low index layers 11, 13, 16, 18, and 20, such thatthe low and high index layers 10-20 can all conduct electricity and/orheat and the index difference between the high and low index regions isgreater than 0.3.

[0015] The arrangement shown in FIG. 1 is a Fabry-Perot device 2,however the invention may be used in other mirror dielectricarrangements. The layers 10-20 of such a device 2 can be separated intothree distinct groups: a top mirror 4, a cavity structure 6 and a bottommirror 8. The top mirror 4 and bottom mirror 8 both include alternatinglayers 10-20 of high and low index materials. The cavity structure 6 maybe made from materials with high indexes. The thickness of each of thelayers 10-20 that form the mirrors 4 and 8 is chosen so that it is aquarter of the wavelength of interest in the material, i.e., thethickness of each layer 10-20 is λ/4n, where λ is the center operatingwavelength in free space, and n is the index of each layer 10-20. Thethickness of the device structure 6 is usually an integer multiple ofλ/2n, to the first order.

[0016] The invention heavily depends on the selection of a low indexmaterial with good electrical and thermal conductivity, which is alsotransparent. One such material is the ITO, as discussed above. Theselection of such a material coupled with the correct doping of thehigher index layer 10, 12, 14, 15, 17, or 19 must follow the followingrelationship for a mirror structure to possess good transmittance, goodelectrical conductivity and good thermal conductivity

E _(g,l) >E _(g,h) >hc/λ  (1)

[0017] where E_(g,h) is the band gap of a high index material, E_(g,l)is the band gap of the low index material, λ is wavelength of light ofinterest, h is Plank constant, and c is the speed of light. Followingrelation (1) guides one to properly select which low index and highindex materials to choose from that does not require trial and error.Relation (1) also guarantees optimal performance of the alternatinglayers of high and low indexes 10-20.

[0018] The index of refraction of ITO is approximately 2, while a highindex material such as doped silicon is about 3.4. This large indexcontrast results in large reflectivity over a wide frequency bandwidthusing just a few layers. Also, the high thermal and electricalconductivity of each layer 10-20 results in tunneling junctions betweenthe two differing materials systems.

[0019] The high index contrast multi-layered structure 2 may befabricated by any of the standard techniques that are used to make othermulti-layered structures. The preferred choice for fabrication is basedon sputtering alternating layers of high and low index materials 10-20.Another technique may be utilizing bonding, smart cut technique orpolishing technique, to achieve the desired for alternating high and lowindex layers 10-20.

[0020] One of the major advantages of using high index contrastmulti-layer mirrors or cavities is that they require much fewer layersthan their low index counter-parts. Also, they are much thinner thantheir low index contrast multi-layer structures. Thus, these structuresare more usable among various integrated components.

[0021] The invention may be used in various applications, such aslasers, tunable filters or mirrors. In a laser or tunable applications,the structure would have one or more electrically active layers that arepumped by electrical injection. The structure can dissipate heat throughthe alternating high and low index materials.

[0022] Although the present invention has been shown and described withrespect to several preferred embodiments thereof, various changes,omissions and additions to the form and detail thereof, may be madetherein, without departing from the spirit and scope of the invention.

What is claimed is:
 1. An optical device comprising: a plurality of high index layers; a plurality of low index layers; wherein said optical device is formed by creating alternating layers of said plurality of high index layers and said plurality of low index layers, such that electricity and heat is conducted through said optical device.
 2. The optical device of claim 1 further comprising that the index difference between said a plurality of high index layers and said plurality of low index layers is greater than 0.3.
 3. The optical device of claim 2, wherein the said plurality of high index layers are Indium Tin Oxides.
 4. The optical device of claim 2, wherein said plurality of high index layers are doped diamonds.
 5. The optical device of claim 2, wherein said plurality of low index layers are doped silicon.
 6. The optical device of claim 2, wherein said plurality of low index layers possess wide band gaps.
 7. The optical device of claim 6, wherein said wide band gaps ensure that the loss in said optical device will be due to scattering off carriers.
 8. The optical device of claim 6, wherein said low index layers exhibit low absorption losses.
 9. The optical device of claim 1, wherein said alternating layers form tunneling junctions between said plurality of high index layer and said low index layers.
 10. The optical device of claim 2, wherein said plurality of high index layers result in large reflectivity over a wide frequency bandwidth.
 11. The optical device of claim 1, wherein said optical device is fabricated by sputtering said alternating layers.
 12. The optical device of claim 1, wherein said optical device is fabricated by bonding.
 13. The optical device of claim 1, wherein said optical device is fabricated by utilizing smart cut technique.
 14. The optical device of claim 1, wherein said optical device is fabricated by utilizing polishing technique.
 15. A method of forming an optical device, comprising providing a plurality of high index layers; providing a plurality of low index layers; wherein said optical device is formed by creating alternating layers of said plurality of high index layers and said plurality of low index layers, such that electricity and heat is conducted through said optical device.
 16. The method of claim 15 further comprising that the index difference between said a plurality of high index layers and said plurality of low index layers is greater than 0.3.
 17. The method of claim 16, wherein the said plurality of high index layers are Indium Tin Oxides.
 18. The method of claim 16, wherein said plurality of high index layers are doped diamonds.
 19. The method of claim 16, wherein said plurality of low index layers are doped silicon.
 20. The method of claim 16, wherein said plurality of low index layers possess wide band gaps.
 21. The method of claim 20, wherein said wide band gaps ensure that the loss in said optical device will be due to scattering off carriers.
 22. The method of claim 20, wherein said low index layers exhibit low absorption losses.
 23. The method of claim 15, wherein said alternating layers form tunneling junctions between said plurality of high index layer and said low index layers.
 24. The method of claim 16, wherein said plurality of high index layers result in large reflectivity over a wide frequency bandwidth.
 25. The method of claim 15, wherein said optical device is fabricated by sputtering said alternating layers.
 26. The method of claim 15, wherein said optical device is fabricated by bonding.
 27. The method of claim 15, wherein said optical device is fabricated by utilizing smart cut technique.
 28. The method of claim 15, wherein said optical device is fabricated by utilizing polishing technique.
 29. A Fabry-Perot device comprising: a plurality of high index layers; a plurality of high index layers; a top mirror that includes alternating layers of said plurality of high index layers and said plurality of low index layers; a cavity structure that includes a bulk of a selective material; and a bottom mirror that includes alternating layers of said plurality of high index layers and said plurality of low index layers; wherein said top mirror and bottom mirror allow electricity and heat to be conducted through said Fabry-Perot device.
 30. A process for forming an optical device, comprising providing a plurality of high index layers; providing a plurality of low index layers; wherein said optical device is formed by creating alternating layers of said plurality of high index layers and said plurality of low index layers, such that electricity and heat is conducted through said optical device.
 31. The process of claim 30 further comprising that the index difference between said a plurality of high index layers and said plurality of low index layers is greater than 0.3.
 32. The process of claim 31, wherein the said plurality of high index layers are Indium Tin Oxides.
 33. The process of claim 31, wherein said plurality of high index layers are doped diamonds.
 34. The process of claim 31, wherein said plurality of low index layers are doped silicon.
 35. The process of claim 31, wherein said plurality of low index layers possess wide band gaps.
 36. The process of claim 35, wherein said wide band gaps ensure that the loss in said optical device will be due to scattering off carriers.
 37. The process of claim 35, wherein said low index layers exhibit low absorption losses.
 38. The process of claim 30, wherein said alternating layers form tunneling junctions between said plurality of high index layer and said low index layers .
 39. The process of claim 31, wherein said plurality of high index layers result in large reflectivity over a wide frequency bandwidth.
 40. The process of claim 30, wherein said optical device is fabricated by sputtering said alternating layers.
 41. The process of claim 30, wherein said optical device is fabricated by bonding.
 42. The process of claim 30, wherein said optical device is fabricated by utilizing smart cut technique.
 43. The process of claim 30, wherein said optical device is fabricated by utilizing polishing technique.
 44. A method of forming a Fabry-Perot device comprising: providing a plurality of high index layers; providing a plurality of low index layers; forming a top mirror that includes alternating layers of said plurality of high index layers and said plurality of low index layers; forming a cavity structure that includes a bulk of a selective material; and forming a bottom mirror that includes alternating layers of said plurality of high index layers and said plurality of low index layers; wherein said top mirror and bottom mirror allow electricity and heat to be conducted through said Fabry-Perot device 